The present invention relates to a current-collecting brush apparatus used for rotary electric equipment such as a dynamo and a motor.
A current-collecting brush apparatus comprises a brush in sliding contact wiht the slip ring or the like part or a rotary electric machine traditionally referred to as a rotor and a pigtail for supplying power to the brush, and is generally installed by being mounted on a brush-holding case. Such a collecting brush apparatus comprises a pigtail including a plurality of strands installed of flexible electrical conductors as disclosed in U.S. Pat. No. 3,577,025. Explanation will be made with reference to the attached drawing about the manner in which a collecting brush apparatus is mounted.
A perspective view of a conventional current-collecting brush apparatus and a holding construction thereof is shown in FIG. 1. In FIG. 1, reference numeral 1 designates a brush, numeral 2 a pigtail with an end secured to the brush, and numeral 3 a brush-holding case for slidably holding the brush 1. The brush-holding case 3 includes a groove 3a. Numeral 4 desigantes a support pillar mounted and locked in the groove 3a, which pillar has a connector 4a for connecting the other end of the pigtail 2 and a brush-supporting arm 4b slidably engaging the brush to guide the brush while placing the brush in position. Numeral 5 designates a U-shaped spring for releasing the lock securing the support pillar 4, and numeral 6 a constant-pressure spring of roll-up type mounted at the lower end of the support pillar 4. The constant pressure spring 6 keeps the upper end of the brush 1 pressed downward thereby to hold the lower side of the brush in contact with the slip ring or rotor 9. Numeral 7 designates a transparent partition plate, numeral 8 an insulating handle for fixing the plate 7, and numeral 10 a bus ring or non-rotating conductor securely bolted to the brush holding case 3 for electrical connection with the pigtail.
The brush 1 is mounted in the manner described below. Specifically, when the brush 1 is not mounted, the constant-pressure spring 6 is located at the lower end of the support pillar 4 in spirally coiled form. The brush 1 is inserted from under the brush-holding case 3, and is mounted by being pushed up while extending the constant-pressure spring 6 against the spring force thereof.
Generally, during the operation of a collecting brush apparatus described above, axial vibrations of the rotary electric machine or the wear or rough surface of the slip ring, etc. causes a spring or bounce of the brush and momentary separation between the brush and the slip ring, unavoidably resulting in a spark generated therebetween. This spark is a source of various adverse effects.